There are a ton of possibilities here to configure different tones on your guitar if you care to experiment.
In this instructable, I'll show how I installed a switch to make both of the humbuckers on my guitar operate as single coils at the same time, but I'll also describe some other options in detail. For example, It is possible to create a single pickup that operates as both a single coil AND humbucker with a control to blend how much of each type of sound is routed through the guitar's controls to the amp. Using a control scheme like this on all of the available pickups would create many tonal variations that can be easily tweaked during a performance. Another possibility, would be to use the pickup as "mostly" single coil to get that single coil tone that is often desired, but use the blend control to dial out some of the characteristic hum at higher gain levels. This would take advantage of the humbuckers hum cancelling properties as much or as little as required for the current volume/gain settings.
In it's simplest form this mod is very easy. If all you want is to turn your humbuckers into single coils you can pull that off in about 20 minutes with nothing more than a small piece of wire! Adding a switch will be more challenging mostly because you need to find a place to put it. You can get a push/pull type potentiometer/switch to replace your volume POT, or you may have to cut a hole in the pick guard to mount a toggle switch. If you intend to blend the two coils you will need a push/pull pot installed in addition to whatever knobs you already have, so make sure you have the necessary space for whatever new components you'll be adding before you blow the money on parts... In my case, there wasn't much room and I didn't have a suitable push/pull POT in my collection, so I added a discrete sliding toggle switch between my existing volume/tone knobs. I had to cut a hole to fit the switch, but I wasn't modding a vintage '56 les paul goldtop or anything! I got this guitar at my local pawn shop for $60! So, take that into consideration when choosing to perform ANY modification. The push/pull volume POT is the way to go to keep this mod reversible if you have an expensive or vintage instrument and still want to make changes to it.